The invention relates to an air bag device for preventing the head of an occupant from being directly hit on a side wall of a vehicle or a side window at a side collision, a roll, or other situations of the vehicle, and more particularly to an air bag device including a curtain shape air bag which, when a high load acts on a side portion of the vehicle, is developed along a roof rail on an inner wall of the vehicle, in an area from the side of a front pillar to the side of a rear pillar across a center pillar.
Conventionally, U.S. Pat. No. 5,778,270 and the like are known as an air bag device in which, when a high load acts on a side portion of a vehicle in a case including a side collision or a roll of a vehicle, an inflator is operated to cause a curtain shape air bag to be developed along a roof rail on an inner wall of the vehicle in an area from the side of a front pillar to the side of a rear pillar, thereby preventing the head of an occupant from being directly hit on a side wall of the vehicle or a side window.
The air bag device disclosed in the U.S. patent specification adopts a configuration in which a number of cylindrical inflatable portions that extend from an upper edge to a lower edge on development so as to be inflated in a cylindrical manner are disposed in parallel to each other over an entire area of the air bag, for the purpose of avoiding a situation that, when the curtain shape air bag is developed, slack is produced in a lower edge portion that is in a free condition, and an intended development area fails to be surely covered, so that an occupant cannot be effectively protected. With this configuration, at the time when the cylindrical inflatable portions are inflated, the surface of the curtain shape air bag is curved in a wavelike form, so as to contract the size in a horizontal direction of the air bag. Thus, the lower edge portion is tensed in the range between the both ends thereof, so that the lower edge portion is substantially fixed in a desired development area.
According to the technique disclosed in the above-identified U.S. patent specification, in addition to the inflatable portions required for protecting an occupant, it is necessary to form a number of cylindrical inflatable portions in order not to produce slack in a lower edge of the curtain shape air bag. Therefore, the number of sewing portions or welding portions is increased and the production cost is increased. In addition, there exists a problem in that an inflator of a larger capacity is required, with the result that also the cost for components is increased.
It is an object of the invention to provide an air bag device in which the number of sewing or welding portions is reduced as compared with the prior art, and in which a curtain shape air bag can be fixed to a desired development position on inflating by using an inflator of a small capacity without producing any slack in a lower edge portion, so that the cost is low and an occupant can be surely protected at the time of a side collision, or the like.
In order to attain the above-mentioned object, the air bag device of the invention is an air bag device including a curtain shape air bag which is developed from a front pillar side to a rear pillar side along a roof rail of an inner wall of a vehicle, by injecting a gas from an inflator which operates when a high load acts on a side portion of the vehicle, and characterized in that a protecting inflatable portion which is inflated by an operation of the inflator to protect an occupant, and at least one cylindrical inflatable portion which communicates with the protecting inflatable portion, and which is inflated in a continuous cylindrical manner from a vicinity of an upper edge to a vicinity of a lower edge of the air bag by the operation of the inflator are disposed in the curtain shape air bag, the curtain shape air bag is accommodated in a folded or wound manner while a plurality of portions of the upper edge of the curtain shape air bag are attached to a plurality of mounting points disposed in the roof rail, one of both end portions of the lower edge is attached to a mounting point disposed in the front pillar side, and another end portion is attached to a mounting point disposed in the rear pillar side, at least one of the mounting points in the front pillar side and the rear pillar side for attaching the both end portions of the lower edge is disposed in a position lower than the mounting points of the roof rail, and the curtain shape air bag is configured so that, in a condition in which the folding or winding is released, slack which elongates across the cylindrical inflatable portion is formed when any gas is not injected, and the cylindrical inflatable portion extends to eliminate the slack at the inflation due to injection of the gas, thereby applying tension to the lower edge of the curtain shape air bag.
In the invention, preferably, at least one of the cylindrical inflatable portions is configured so as to be inflated while interfering with a center pillar at the injection of the gas. In the invention, a configuration in which the curtain shape air bag is accommodated in a wound manner in which the lower edge is directed to an inner side of the vehicle can be preferably adopted.
Moreover, as the curtain shape air bag in the invention, a curtain shape air bag in which an inflatable portion that continuously extends along the lower edge is formed can be used. The continuous inflatable portion extending along the lower edge can be configured so as to form a gas passage for linking the cylindrical inflatable portion to the inflator.
Furthermore, in the invention, a gas passage for enabling the inflator to directly communicate with one of the cylindrical inflatable portions may be formed so that the gas from the inflator is first injected into the cylindrical A inflatable portion.
In addition, the invention can adopt a configuration in which, in the curtain shape air bag, mounting portions to the mounting points of the vehicle excluding both end portions of the lower edge are loosely attached to the respective mounting points via slots which are formed correspondingly to the mounting points, thereby enabling extension in inflation of the cylindrical inflatable portion. Alternatively, the invention can preferably adopt a configuration in which a slit or a cutout is formed in a predetermined position of the curtain shape air bag, thereby enabling extension in inflation of the cylindrical inflatable portion.
Unlike the prior art in which tension is applied by inflating a number of cylindrical inflatable portions disposed in a curtain shape air bag so as to contract a lower edge portion, the invention adopts a configuration in which a gas from an inflator is injected into one or several cylindrical inflatable portions which are formed continuously from the vicinity of the upper edge to the vicinity of the lower edge of a curtain shape air bag, so as to cause the cylindrical inflatable portion(s) to extend, and the lower edge of the curtain shape air bag in which both of lower edge end portions are fixed to the car body is stretched due to the extension, so as to apply tension to the lower edge, thereby attaining the intended object.
Specifically, in the curtain shape air bag in the invention, an upper edge portion is fixed in a plurality of positions to mounting points of the roof rail, one of the lower edge end portions is attached to a mounting point disposed on the front pillar side, and the other lower edge end portion is attached to a mounting point disposed on the rear pillar side. In addition, at least one of the mounting points for attaching the lower edge end portions is disposed in a lower position than the roof rail. The curtain shape air bag in a naturally attached condition (in a condition in which the folding or winding is released, and a condition in which any gas is not injected) produces slack which elongates across the cylindrical inflatable portions, and is accommodated in a folded or wound manner along the roof rail. When a gas from the inflator is injected into the cylindrical inflatable portions of the curtain shape air bag and the portions are inflated, the cylindrical inflatable portions extend so as to eliminate the slack and to push down part of the lower edge of the curtain shape air bag, because the cylindrical inflatable portions elongate from the vicinity of the upper edge to the vicinity of the lower edge of the curtain shape air bag. Under a state where both ends of the lower edge of the curtain shape air bag are respectively fixed to the mounting points, therefore, forming portions of the cylindrical inflatable portions are pulled downwardly, and tension acts on the lower edge portion, so as to be fixed in a regular position. The protecting inflatable portion into which the gas from the inflator is injected together with the cylindrical inflatable portions is inflated in a desired position, so as to protect an occupant.
When the configuration of the invention in which the cylindrical inflatable portions for applying tension to the lower edge of the curtain shape air bag are inflated while interfering with the center pillar is employed, even in the case where a side window is opened, the curtain shape air bag will not go out of a vehicle compartment via the side window, thereby attaining the above-mentioned functions and effects, so that an occupant can be surely protected.
Moreover, when the configuration of the invention in which the curtain shape air bag is accommodated in a wound manner so that the lower edge is directed to the inside of the vehicle is employed, the development of the curtain shape air bag in the extending condition of the cylindrical inflatable portions is smoothly performed along the inner side face of the vehicle. When used in combination with the configuration of the cylindrical inflatable portions for applying tension to the lower edge of the curtain shape air bag are inflated while interfering with the center pillar, the curtain shape air bag is developed downwardly while being guided by the center pillar even when the side window is opened, so that an occupant can be surely protected.
In the configuration of the invention in which the continuous inflatable portion is formed along the lower edge of the curtain shape air bag, the lower edge of the curtain-shape air bag becomes three dimensional on being inflated, and high rigidity is generated by a synergistic effect with the tension acting on the lower edge due to the extension of the cylindrical inflatable portions. In addition, the continuous inflatable portion of the lower edge is fitted between a seat and a door or an inner side wall, so as to play a roll for further enhancing the fixing effect of the position of the curtain shape air bag.
In a further embodiment, the above-mentioned continuous inflatable portion extending along the lower edge of the curtain shape air bag is used as the gas passage for linking the cylindrical inflatable portions to the inflator. When the curtain shape air bag is inflated, therefore, while the inflatable portion extending along the lower edge is first inflated, the cylindrical inflatable portions are inflated, so as to apply tension to the inflatable portion of the lower edge. Accordingly, the curtain shape air bag can be rapidly continuously developed from the folded or wound accommodated condition to a desired position, to be set into a fixed condition.
On the other hand, in yet another embodiment where the cylindrical inflatable portions for applying tension to the lower edge of the curtain shape air bag, the gas passage for directly injecting a gas from the inflator is formed. Accordingly, the downward development of the curtain shape air bag is rapidly performed, and at the same time tension can be promptly applied to the lower edge, so as to fix the position thereof. In addition, even if the inflator is disposed in an arbitrary position, the functions and effects can be attained.
The invention of an element for enabling the cylindrical inflatable portions of the curtain shape air bag to smoothly extend at the time of injection of the gas is additionally provided. Slots are disposed respectively in the plurality of mounting portions for the vehicle and disposed in an upper edge of the curtain shape air bag, and the curtain shape air bag is attached to the mounting points of the vehicle in a loose manner via the respective slots. When the gas is injected into the cylindrical inflatable portions, accordingly, the mounting portions are appropriately moved, thereby enabling the cylindrical inflatable portions to smoothly extend. On the other hand, a slit or a cutout is formed in a predetermined position of the curtain shape air bag. When a gas is injected into the cylindrical inflatable portions, therefore, the slit or the cutout is widened, thereby enabling the cylindrical inflatable portions to smoothly extend. In the invention, the characteristic configurations of slots and a slit or a cutout can be used in combination.